1) Field of the Invention
The present invention relates to a cooling fan motor drive apparatus for vehicles, which is made to drive vehicle cooling fan motors upon receipt of a power supply voltage through a power supply line.
2) Description of the Related Art
In a vehicle (such as a car), there is provided a cooling fan for cooling a radiator of an engine and condenser of an air conditioner, and so far, such a cooling fan has been rotationally driven by a motor (for example, DC motor). FIG. 12 is an illustration of an electrical arrangement of a drive apparatus designed to drive two cooling fan motors in series/in parallel. In FIG. 12, a drive apparatus 1 employs a mainstream approach, made to drive cooling fan motors 2 and 3 in series or in parallel through the use of three relays according to cooling capability needed.
That is, a power supply line 4 is connected through an ignition switch (not shown) to a positive-side terminal of a battery, and one terminal of each of exciting coils 6a, 7a and 8a of the relays 6, 7 and 8 is connected through a fuse 9 to the power supply line 4. The other terminal of each of the exciting coils 7a and 8a is connected to the ground 12 through a water temperature switch 10 and an air conditioner high-pressure switch 11 placed in parallel with each other. Moreover, the other terminal of the exciting coil 6a is connected through an air conditioner amplifier 13 having an equivalent circuit illustrated and a switch 14 to the ground 12, and further connected through the air conditioner 13 to the water temperature switch 10 and the air conditioner high-pressure switch 11. To the air conditioner amplifier 13, a battery voltage is supplied from the power supply line 4 through a fuse 15, and the switch 14 takes a make-and-break action in conjunction with a magnet clutch (not shown).
Between a power supply line 16 connected directly to the positive-side terminal of the battery 5 and the ground 12, there are formed a series circuit comprising a fuse 17, a relay switch 6b, a cooling fan motor 2 and a relay switch 7b (at the on-condition of the normally-open contact) and a series circuit comprising a fuse 18, a relay switch 8b and a cooling fan motor 3. The normally-closed contact of the relay switch 7b is connected to the cooling fan motor 2.
In this drive apparatus 1, the operations of the cooling fan motors 2 and 3 in the states of the water temperature switch 10, the air conditioner high-pressure switch 11 and the switch 14 (magnet clutch) are as shown in FIG. 13. That is, the cooling fan motors 2 and 3 come to a stop when all the switches are in the off-condition, while they are drive in series when the switch is in the on-state and the air conditioner high-pressure switch 11 and the switch 14 are in the off-state, and driven in parallel when the water temperature switch 10 or the air conditioner high-pressure switch 11 is in the on-state.
The cooling fan motors 2 and 3 are located close to a condenser and radiator existing in the front part of a vehicle, and for simplifying the handling of a harness with respect to the cooling fan motors 2 and 3 and for reducing the loss in the harness, it is desirable that the drive apparatus is put in the vicinity of the cooling fan motors 2 and 3. However, since the front part of a vehicle is exposed to bad environments because of being dashed with liquid or dust by the running of the vehicle, for installing the drive apparatus 1 therein, there is a need to place the relays 6, 7 and 8 constituting the drive apparatus 1 in a dedicated relay box and reinforce the sealing structure. However, since the reinforcement of the sealing structure is costly, in the present circumstance the drive apparatus 1 is required to be located at a position (for example, the rear surface side of the engine room) remote from the cooling fan motors 2 and 3 and exposed to less liquid and dust.
In addition, since the drive apparatus 1 is composed of the fuses 9, 15, 17, 18 and the relays 6, 7, 8, for example, if the one cooling fan motor 2 is locked during the driving of the vehicle, the fuse 17 is fused so that the cooling fan motors 2 and 3 can be driven only when the fuse 17 is replaced with new one. Accordingly, once the motor lock occurs, difficulty is experienced in operating the cooling fan motors 2 and 3 even if it is released therefrom. Still additionally, in high-temperature and high-pressure conditions, only the other cooling fan motor 3 is driven to produce the lack of cooling capability, thus readily causing the overheating or the lowering of the performance of the air conditioner.
The present invention has been developed in consideration of the above-mentioned situations, and it is therefore an object of the invention to provide a cooling fan motor drive apparatus for use in a vehicle, capable of being placed close to vehicle cooling fan motors and, even if the cooling fan motor falls temporarily into an abnormal condition, capable of being restored to its normal condition after the recovery thereof.
For this purpose, according to the present invention, in a cooling fan motor drive apparatus for use in a vehicle which drives cooling fan motors upon receipt of a power supply voltage through a power supply line, first to fourth semiconductor switches are provided, and control means closes the second and fourth semiconductor switches to establish a current-carrying path extending from a first power supply line through the second semiconductor switch, a second vehicle cooling fan motor, the fourth semiconductor switch and a first vehicle cooling fan motor to a second power supply line so that the first and second vehicle cooling fan motors are driven in series, while the control means closes the first, second and third semiconductor switches to establish a current-carrying path extending from the first power supply line through the first semiconductor switch and the first vehicle cooling fan motor to the second power supply line and a current-carrying path extending from the first power supply line through the second semiconductor switch, the second vehicle cooling fan motor and the third semiconductor switch to the second power supply line so that the first and second vehicle cooling fan motors are driven in parallel.
As mentioned above, this drive apparatus is designed to switch the vehicle cooling fan motors between the serial and parallel operations and, hence, the semiconductor switches are easily configured into a sealed condition by means of resin molding or the like and the size reduction is further attainable in comparison with the conventional construction using relays. This enables the drive apparatus to be located in the vicinity of the cooling fan motors where the mounting space is difficult to secure and much dashed liquid and dust exist, which simplifies the handling of the harness with respect to the cooling fan motors and reduces the loss in the harness. Moreover, the employment of the semiconductor switches prevents damages and permits protection from overload, protection from overcurrent and protection from malfunction due to noises, and even if the cooling fan motor falls temporarily into an abnormal condition, it can be restored to a normal operation after the recovery from the abnormal condition.
In addition, in the drive apparatus according to the present invention, a reference current is set in accordance with a serial or parallel operation condition, and when a current flowing in the cooling fan motor exceeds the reference current, an output of a current-excess signal takes place. There is a situation that the operation of the cooling fan motor is required to be maintained to the utmost and it is undesirable that the operation thereof comes to a stop during the parallel operation which particularly requires a high cooling capability. Still additionally, considering the case that abnormality, for example, locking, occurs in the cooling fan motor, when the parallel operation is conducted, all the power supply voltage is applied to a motor resistor so that there is a possibility that an extremely large current flows, while at the serial operation the cooling fan motor taking an non-locked condition undertakes the power supply voltage so that the current is relatively suppressible. Therefore, when the switching from the parallel operation to the serial operation is made provided that a current-excess signal is outputted at the parallel operation, it is possible to continue the cooling while maintaining the cooling capability to some extent even in the case of the occurrence of abnormality.
Moreover, in the drive apparatus according to the present invention, when a current detection signal continues for over a predetermined time period and exceeds a current reference signal, a current-excess signal is outputted to make the switching from the parallel operation to the serial operation. This prevents the actually unnecessary switching to the serial operation from being made in a case in which an excessive rush current flows temporarily due to the switching from the serial operation to the parallel operation or in a case in which an erroneous current-excess signal is outputted due to noises or the like, thus achieving stable operations.
Still moreover, in the drive apparatus according to the present invention, the switching to the serial/parallel operation condition before the output of the current-excess signal is made provided that the output of the current-excess signal comes to a stop, which secures the cooling capability to the utmost in the case of a high cooling capability being required.
Furthermore, in the drive apparatus according to the present invention, when the current detection signal continues for over a predetermined time period and does not exceed the current reference signal, the output of the current-excess signal is stopped and the switching to the serial/parallel operation condition before the output of the current-excess signal is made, thereby preventing the hunting phenomenon that the serial operation and the parallel operation are frequently conducted repeatedly.
Still furthermore, in the drive apparatus according to the present invention, the control means conducts the serial operation only for a predetermined time period at the start-up irrespective of a selection command for the serial/parallel operation to produce speed electromotive forces in the first and second cooling fan motors and then makes the switching to the parallel operation according to the selection command, thus reducing the rush current at the start-up in comparison with the start-up in the parallel condition.
In addition, in the drive apparatus according to the present invention, reflux means is connected to the first to fourth semiconductor switches in parallel, thus suppressing the occurrence of the surge voltage occurring at the switching of the semiconductor switch from the on-condition to the off-condition.
Still additionally, in the drive apparatus according to the present invention, in a case in which a rotational force is given to the cooling fan motor while it catches wind, for example, in a state where the vehicle is running and the power supply voltage drops below a predetermined voltage, when the control means opens the first to third semiconductor switches and closes the fourth semiconductor switch so that a current flows through a path extending from the second power supply line through the first cooling fan motor, the fourth semiconductor switch, the second cooling fan motor and the reflux means connected in parallel with the second semiconductor switch to the first power supply line to accomplish the regeneration of power on the power supply line side. This improves the power balance.